Non-aqueous lithium electrochemical cells typically include an anode, a lithium electrolyte prepared from a lithium salt dissolved in one or more organic solvents and a cathode of an electrochemically active material, typically a chalcogenide of a transition metal. During discharge, lithium ions from the anode pass through the liquid electrolyte to the electrochemically active material of the cathode where the ions are taken up with the simultaneous release of electrical energy. During charging, the flow of ions is reversed so that lithium ions pass from the electrochemically active cathode material through the electrolyte and are plated back onto the lithium anode. Non-aqueous lithium electrochemical cells are discussed in U.S. Pat. Nos. 4,472,487, 4,668,595, 5,028,500, 5,441,830, 5,460,904, 5,540,741, and 5,584,893.
Recently, the lithium metal anode has been replaced with a carbon anode such as coke or graphite intercalated with lithium ions to form Li.sub.X C. In operation of the cell, lithium passes from the carbon through the electrolyte to the cathode where it is taken up just as in a cell with a metallic lithium anode. During recharge, the lithium is transferred back to the anode where it reintercalates into the carbon. Because no metallic lithium is present in the cell, melting of the anode does not occur even under abuse conditions. Also, because lithium is reincorporated into the anode by intercalation rather than by plating, dendritic and spongy lithium growth does not occur.
Laminate cells and batteries have been developed which possess good performance characteristics. Typically, a laminate cell includes composite electrodes which refer to cathodes and anodes wherein the cathode is comprised of materials other than compatible cathodic materials and the anode is comprised of materials other than compatible anodic materials. Typically, the composite electrodes contains a polymer which acts to bind the composite materials together and an electrolytic solvent. Composite electrodes are well known in the art. For example, a composite cathode can comprise a compatible cathodic material, a conductive material, an electrolytic solvent, an alkali salt, and a solid matrix forming polymer. Similarly, for example, a composite anode can comprise a compatible intercalation anodic material, an electrolytic solvent and a solid matrix forming polymer.
In order to enhance the overall current produced by solid or liquid batteries, it is conventional to employ several electrochemical cells in a battery. When so employed, the current from each of the cells is accumulated so that the total current generated by the battery is roughly the sum of the current generated from each of the individual electrochemical cells employed in the battery. One method for accumulating the current from individual electrochemical cells is by using a current collector attached to the cathode or the anode of the electrochemical cell. Typically, the current collector is a metal foil or a conductive plastic which is coupled to other current collectors in the battery so that the current generated by each cell is collected and accumulated over all of the cells. Thus, the total current generated by the battery is a summation of the current generated by each of the electrochemical cells employed in the battery minus whatever current is lost due to resistance in the current collector. Current collectors are described, for example, in U.S. Pat. Nos. 4,925,752, 5,011,501, and 5,441,830. Notwithstanding the benefits of using current collectors in electrochemical cells, metal foil current collectors often do not adhere to the surface of composite electrodes. This inevitably reduces the electrochemical performance of the electrochemical cell and battery. U.S. Pat. No. 5,464,707 describes the use of an adhesion promoting layer that is applied onto the surface of a current collector. Thereafter, a cathode paste comprising monomers and/or prepolymers is coated onto the adhesion layer. Upon curing the monomers and/or prepolymers of the cathode paste, the cathode material becomes attached to the collector.